Abstract: For improving security of traffic and pedestrian, the paper introduced a design scheme of crossing alarming system, gave overall structure, selection of single chip microcomputer, sensor detecting circuit, active shield driving circuit, signal processing circuit and software design method of the system. The system can alarm after detecting train signal and display the train rate and approaching direction in order to alert pedestrians. The testing result showed the system can alarm for 1 min accurately when the train is less than 1 km away from crossing with high anti-interference ability and stability.